Users today generally subscribe to two types of communication systems; namely, fixed line communication systems and cellular communication systems. Cell phones are typically used on-the-go, and fixed phones are typically used in homes and offices. Fixed phones are known to have better sound quality, and their use is less expensive than cell phones.
Many subscribers use cordless phones in their homes. A cordless phone is a wireless unit that communicates via radio waves with a base station that is connected to a fixed telephone line. A cordless phone is operable within a limited range of its base station. The base station attaches to a telephone network in the same way that a conventional corded phone attaches thereto. A cordless phone uses one of a variety of communication protocols, such as Digital Enhanced Cordless Telecommunications (DECT), Personal Handyphone System (PHS) and Bluetooth, each standard differing in frequency band and method of transmission.
When subscribers are in range of their base stations, they are able to communicate using both a cordless phone and a cellular phone. Since cordless phones enjoy the benefits of fixed phones, it is of advantage to subscribers to integrate their cordless phones and cell phones, and have incoming calls to their cell phones forwarded to their cordless phones when the subscribers are in range of their base stations. It is also of advantage to network operators to integrate cordless phones and cell phones. Subscribers benefit by being able to use their cordless phones instead of their cell phones wherever possible. Operators who own both fixed and cellular networks benefit by reductions in traffic over the cellular network.
Prior art stations for integrating cordless and cell phones, such as KX-TH1211 and KX-TH1212, manufactured by Panasonic Corporation of Osaka, Japan, and GE28128EE2, manufactured by General Electric Company of Fairfield, Conn., use “Link-to-Cell” technology. In this regard, reference is now made to FIG. 1, which is a prior art diagram of a combined DECT+cellular system for integrating a cordless phone and a cell phone. As shown in FIG. 1, a cell phone is connected to a single Link-to-Cell base station via Bluetooth, and may be placed anywhere in a vicinity of the base station, ideally in an area with good cellular coverage. When an incoming cellular call is received, the base station rings the cordless phone.
A similar system, the Bluetooth Cell Phone Docking Station ITC-BTTN, manufactured by XLink Technology, Inc. of Milpitas, Calif., operates by connecting a Bluetooth-enabled cell phone with a standard desktop phone, enabling a subscriber to use a regular home or office phone over a cellular service network.
Subscribers often store large amounts of personal data on their cell phones, including inter alia information about contacts, calendar items, themes, ring tones, music and documents. Cordless phones, in distinction, typically store little or none of the subscribers' personal data. As such, use of cordless phones is limiting for subscribers.
U.S. Pat. No. 7,043,248 to Hallenstal et al. describes a mobile terminal that combines a cordless+cell phone. Incoming calls to a phone number of the mobile terminal are connected over a fixed line network if the mobile terminal is within radio coverage of a home base station, and connected over a cellular network if the mobile terminal is out of radio coverage. As such, network operators direct calls over the fixed line network instead of the cellular network, thereby relieving congestion of the cellular network.
According to Hallenstal, the home base station periodically updates the mobile terminal as to whether the subscriber is within range of the base station. This information is stored in an operator database, such as the location database of the fixed line operator, or the home location register (HLR) of the cellular operator.
According to Hallenstal, a subscriber has a single phone number in both cellular and fixed line networks, and thus when an incoming call arrives, the database storing information about the subscriber's location is queried to determine whether the call should be routed via the fixed line network or via the cellular network.
A drawback with the system of Hallenstal is the need for a single phone that is compatible with both the home base station technology, such as DECT, and with the cellular network technology. A further drawback with the system of Hallenstal is incompatibility with existing phone systems.
CSR PLC of Cambridge, England and IVT Corporation of Beijing, China have announced a one-phone combination cordless+cellular system, based on Bluetooth technology. The one-phone combination uses the Cordless Telephony Profile (CTP) within Bluetooth, to enable a Bluetooth-enabled cell phone to switch between cellular and fixed line networks, depending on the subscriber's location. The one-phone combination uses a single phone number for both cellular and fixed line network connections.
A drawback with the one-phone combination is that a single device is generally not suitable for both home/office use and for on-the-go use.